Metallurgical Tests in Endodontics: A Narrative Review

Since there are no reviews of the literature on this theme, the aim of this narrative review is to summarize the metallurgical tests used in endodontics, pointing out their functional use and their pros and cons and giving readers a user-friendly guide to serve as an orientation aid in the plethora of metallurgical tests. With this purpose, a literature search for articles published between January 2001 and December 2021 was conducted, using the electronic database PubMed to collect all published articles regarding the metallurgical tests used in endodontics for the evaluation of NiTi rotary instruments. The search was conducted using the following keywords: “metallurgy”, “differential scanning calorimetry” (DSC), “X-ray diffraction” (XRD), “atomic force microscopy” (AFM), “energy-dispersive X-ray spectroscopy” (EDS), “focused ion beam analysis” (FIB) and “Auger electron spectroscopy” (AES) combined with the term “endodontics” or “NiTi rotary instruments”. Considering the inclusion and exclusion criteria, of the 248 articles found, only 81 were included in the narrative review. According to the results, more than 50% of the selected articles were published in one of the two most relevant journals in endodontics: International Endodontic Journal (22.2%) and Journal of Endodontics (29.6%). The most popular metallurgical test was DSC, with 43 related articles, followed by EDS (33 articles), AFM (22 articles) and XRD (21 articles). Few studies were conducted using other tests such as FIB (2 articles), micro-Raman spectroscopy (4 articles), metallographic analysis (7 articles) and Auger electron spectroscopy (2 articles).

Perspectives on Light-Based Disinfection to Reduce the Risk of COVID-19 Transmission during Dental Care

Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) is a positive-sense single-stranded RNA coronavirus capable of causing potentially lethal pneumonia-like infectious diseases in mammals and birds. The main mechanisms by which SARS-CoV-2 spreads include airborne transmission (aerosols and droplets) and the direct exposure of tissues (conjunctival, nasal, and oral mucosa) to contaminated fluids. The aerosol formation is universal in dentistry due to the use of rotary instruments (handpieces), ultrasonic scalers, and air–water syringes. Several layers of infection control should protect key stakeholders such as dentists, dental staff, and patients. These include the utilization of personal protective equipment, high-volume evacuation systems, pre-procedural mouthwashes, rubber dam, and more recently, antimicrobial photodynamic therapy and intra-oral visible light irradiation. These non-specific light-based approaches are relatively simple, inexpensive, and effective against viruses, bacteria, and fungi. Therefore, the present perspective review discusses the current efforts and limitations on utilizing biophotonic approaches as adjunct infection control methods to prevent the transmission of SARS-CoV-2 in dental settings. In addition, the present perspective review may positively impact subsequent developments in the field, as it offers relevant information regarding the intricacies and complexities of infection control in dental settings.

An Update on Nickel-Titanium Rotary Instruments in Endodontics: Mechanical Characteristics, Testing and Future Perspective—An Overview

Since the introduction of Nickel-Titanium alloy as the material of choice for the manufacturing of endodontic rotary instruments, the success rate of the root canal therapies has been significantly increased. This success mainly arises from the properties of the Nickel-Titanium alloy: the biocompatibility, the superelasticity and the shape memory effect. Those characteristics have led to a reduction in time of endodontic treatments, a simplification of instrumentation procedures and an increase of predictability and effectiveness of endodontic treatments. Nevertheless, the intracanal separation of Nickel-Titanium rotary instruments is still a major concern of endodontists, with a consequent possible reduction in the outcome rate. As thoroughly demonstrated, the two main causes of intracanal separation of endodontic instruments are the cyclic fatigue and the torsional loads. As results, in order to reduce the percentage of intracanal separation research and manufacturers have been focused on the parameters that directly or indirectly influence mechanical properties of endodontic rotary instruments. This review describes the current state of the art regarding the Nickel-Titanium alloy in endodontics, the mechanical behavior of endodontic rotary instruments and the relative stresses acting on them during intracanal instrumentation, highlighting the limitation of the current literature.

Role of the Crystallographic Phase of NiTi Rotary Instruments in Determining Their Torsional Resistance during Different Bending Conditions

The aim of this study was to assess the role of the crystallographic phase of Nickel-titanium (NiTi) rotary instruments in determining their torsional resistance during different bending conditions, such as different degrees and angles of curvature. 200 F-One 20.04 instruments (Fanta Dental, Shanghai, China) were used, 100 austenitic instruments and 100 martensitic instruments. Each group was divided in 5 subgroups according to the different bending conditions (straight canal, 90° or 60° of curvature degrees and 3 mm or 5 mm of radius of curvature). The static torsional test was performed by using a device composed of an electric motor capable of recording torque values (N·cm); a vice used to secure the instruments at 3 mm from the tip; and artificial canals, which allow instruments to remain flexed during test. Each instrument was rotated at 500 rpm with a torque limit set to 5.5 Ncm until its fracture. Torque at Fracture (TtF) was registered. A scanning electron microscopy (SEM) observation was conducted. The collected data confirm that an increase in the angle of curvature and a decrease in the radius of curvature of the artificial canals lead to an increase of TtF values with a statistically significant difference (p < 0.05), both in the austenitic and martensitic groups. Regarding the comparison between austenitic and martensitic groups in the same bending condition, a statistically significant difference was found only when the torsional test was performed in the canals with the degrees of curvature of 90° and the radius of curvature of 3 mm and 5 mm, with the austenitic instruments showing a higher TtF than the martensitic ones. In conclusion, it can be stated that the crystallographic phase influences the maximum torque at fracture when the instruments are subjected to severe bending and that the radius of curvature significantly influences their torsional resistance.

Endodontic instruments fracture in root canal: Integrative review

Introduction: Endodontic instruments fracture is related to several factors from internal dental anatomy and type, to operator inability and inexperience. Objective: To review case reports related to fracture of endodontic instruments inside the root canal. Methodology: A literature review was carried out using papers available in the PubMed and Lilacs databases. Only case reports were included, with no restriction on language and publication year Results: It was analyzed eight papers with 11 instrument fracture cases, with the highest prevalence (45.5%) of rotary instruments fracture, occurring mainly in middle-cervical and middle-apical root canals thirds. In 90.9% of cases, techniques used for removal showed successful results and in only one case (9.1%), the technique was unsuccessful and the instrument was kept inside the root canal. Final considerations: Endodontic instruments fracture is a complication can directly affect prognosis and endodontic treatment success. Several techniques and devices can be used to remove fractured fragments inside root canals, however, there is no specific protocol for their removal. Keywords: accidents; endodontics; fracture; dental instruments; prognosis.

Introduction of nickel titanium rotary instruments to undergraduate students

Many studies address the quality of root canal treatments, but few refer to endodontics using rotatory techniques performed by novice operators. This study evaluated the performance of undergraduates in their first contact with rotary root canal instrumentation concerning the findings of the final periapical radiograph, and the post endodontic treatment pain. A longitudinal observational study was performed on periapical radiographs of 491 teeth from 450 patients submitted to root canal treatment by undergraduate students from 2015 to 2018. The analysis of the length of root canal filling followed the criteria: (i) acceptable, if periapical radiograph presents root filling ending 0 - 1 mm short of radiographic apex; (ii) over, if periapical radiograph presents root filling ending beyond the radiographic apex; and (iii) under, if periapical radiograph presents root filling ending > 1 mm short of radiographic apex. Evaluation of postendodontic treatment pain was categorized into either absence or presence of pain. Adequate length root canal filling was observed in 65.9% of the cases (324 teeth). Periapical lesions presence and dimensions did not interfere to the obturation quality. Statistical relation was found between the pulp condition and postendodontic treatment pain. The presence of pain was observed in 4.7% of the vital teeth and 0.3% of non-vital teeth. The presence of periapical lesion did not influence postoperative pain. Adequate length root canal filling was observed in most cases and NitTi rotary instrumentation had applicability in undergraduate programs, even with novice operators. Besides that, pulp condition had an effect on postendodontic pain.

In Vitro Evaluation of a Recently Developed Rotary File: AF Rotary

Objective: Aim of the present study is to evaluate mechanical properties of a newly developed rotary file, AF Rotary (Fanta Dental, Shanghai, China), and to compare these features with a worldwide spread rotary file, Protaper Gold F2 (PTG F2; Dentsply Maillefer, Ballaigues, Switzerland). Material and Methods: 60 AF Rotary 25.06 and 60 PTG F2 were divided in three groups of 20 files each. A group underwent to cyclic fatigue resistance tests, second group underwent to torsional resistance tests, third group underwent to bending tests. The statistical analysis was performed using t student test with significance level set at 95% (p < 0.05). Results: AF Rotary showed significantly higher torsional resistance and cyclic fatigue resistance (p < 0.05) when compared to the PTG F2. AF Rotary also showed significantly lower bending resistance (p < 0.05) when compared to the PTG F2. Conclusion: Therefore, within the limitations of this study, the results show better performances for AF Rotary compared to PTG F2 regarding the cyclic fatigue test, the torsional test and the bending test. Since the PTG F2 is a commonly used and widely investigated instrument it could be possible to state that the AF Rotary exhibits remarkable in vitro performances. Keywords AF Rotary; Protaper gold; NiTi rotary instruments; Cyclic fatigue; Torsional resistance.

Torsional Resistance of Heat-Treated Nickel-Titanium Instruments under Different Temperature Conditions

This study compared the torsional resistance of heat-treated nickel-titanium (NiTi) instruments under different temperature conditions. Four thermomechanically treated single-use NiTi rotary instruments were selected for this study: OneShape (OS), OneCurve (OC), WaveOne Gold (WOG) and HyFlex EDM (HFE). Each instrument was further subdivided by temperature into 2 subgroups. Maximum torque and the distortion angle until fracture occurred were evaluated. Differential scanning calorimetry analysis was performed to measure the phase transformation temperature. Statistical analysis was performed using a two-way ANOVA and t-test (p < 0.05). Fractured fragments were observed using scanning electron microscopy (SEM). The two-way ANOVA showed no significant differences for different temperature conditions. At both room (RT) and body temperature (BT), OS was predominantly austenite while HFE was martensite. OC and WOG were predominantly martensite at RT and mixed phase at BT. At BT, more than half of WOG was martensite, while half of OC was austenite. SEM examination showed no topographical differences between instruments in different temperature groups. In relation to a limitation of this study, there was no difference in torsional resistance of NiTi rotary instruments between the BT and RT conditions. This implies that clinicians do not need to consider a decrease of torsional resistance of heat-treated NiTi instruments at BT.